An optical transmission medium bend working device that reduces bending loss of an optical transmission medium includes: an arc-discharge electrode that partially and sequentially heats a bend working area of a tape core wire in an up-down direction, the tape core wire extending in the up-down direction with a distal end thereof being located on a lower side, the bend working area being located above the distal end; a core wire holding unit that holds a portion of the tape core wire located above the bend working area; and a bending arm that applies force to the tape core wire in a state where the bend working area is heated to bend the tape core wire at the bend working area.